Understanding the balance between trim, speed, and water conditions can have you saving money at the fuel pump
If I could tell you how to save money on fuel, increase top speed, and have a smoother ride in your boat, at no extra cost, would you be interested? I would imagine the answer is ‘yes.’
To do this, it is all about correctly operating a key control switch for your motor. Lets look at this, one step at a time.
Saving money on fuel: this one is easy to follow.
The greater the area of the boat surface that is in contact with the water, the greater the friction between the boat and the water. Greater friction means the engine must work harder, so if you can reduce friction, you decrease the engine load. When an engine does not work as hard, it uses less fuel, so it is possible to operate your boat with lower fuel expenses by simply reducing your boat’s wetted surface.
The next time you are driving your boat, try experimenting with your trim toggle switch, located at the top of your throttle. You should always start from a dead stop with your trim fully down but once on plane you must raise it, at least a little. Now here is the experiment:
Begin with neutral trim or close to “down” trim. Then press the “up” side of your trim toggle switch for half a second. You will see your bow rise slightly. After one second repeat the half second “up” press on your trim toggle. By repeating this process, at one point you will actually feel your boat pop itself a little more free from the water. It will be like your boat suddenly becomes less stuck to the water. After doing this a few times, you will come to recognize the “feel” of your boat loosening it’s friction with the water. With this “higher trim setting” your boat is now using less fuel.
Better top speed: have you ever wondered why the guy down the lake, with the same boat and power as you, seems to go faster?
It could be the same friction problem as described above, meaning too much boat contact with the water relative to contact with the air. The solution here is similar but extended. Press the “up” side of your trim toggle switch repeatedly for one half second at a time. You will notice your speed increase substantially. Your boat will first free itself a little, and then as you continue the “up” trim process the bow, that was just rising a moment ago, will drop slightly. Then it will rise again, repeating a process that we call porpoising. Here’s what happens: when the bow up pressure that you apply with your toggle switch fails to be sufficient to overcome the pressure of gravity, pressing your bow down, the result will be porpoising. You have trimmed “up” slightly too far. As soon as this occurs, press down on your toggle switch for one second. The porpoising will stop and you will be at your boat’s maximum speed.
Before you challenge the guy down the lake, it is important that you make note of your engine RPM’s when your boat is trimmed to this maximum speed. The RPM number that you read should match the maximum RPM level recommended by your engine manufacturer. If it is higher, you might get an even higher speed with a larger pitch propeller. This will also put your engine RPM within the recommended range. If the number is lower than recommended, you may be over propped and a slightly lower pitch or different style prop will give you more speed. Make sure you understand how to find your best propeller.
A smoother ride: okay, that’s the trim magic that will save fuel costs and help your boat go faster, but how can a trim control make your ride smoother? When you are driving your boat on totally flat water, the quality of the ride will not vary with the speed you are travelling. But, when driving your boat on choppy water, or anything other than ‘flat,’ the interaction between your boat and the water will change with each different water condition. These interactions will also vary with the length and type of boat you drive. It is no surprise that longer boats generally ride smoother than shorter ones. That is because they “bridge” short wave patterns, rather than partially dipping into troughs between the crests. When your boat dips and hits an oncoming wave, you feel the thump. This is why longer boats have a comfort advantage. This is also why it is important to understand waves and wakes.
While it is not practical to own a fleet of boats that allow you to choose the optimum length for differing sea conditions, there is something else that you can change. Your speed. While it is logical that when the going gets bumpy you should slow down, it is not so obvious that speeding up can also mitigate the effects of choppy water. Increasing speed will raise the horizontal operating level of your boat and this could result in less of your boat hitting the tops of waves. Note that both slowing down and speeding up will change how your boat interacts with the water surface.
While altering speed is an important way to handle rough water, there is another very important method. Yes, we go back to your trim control. There are truly very few water conditions for which you cannot improve the quality of your boat ride by using a combination of trim control and speed adjustment. The next time your boat is running like a rocking horse or jarring your spine with a series of mini-hits, remember to experiment with speed and trim. Try adding a little “up” trim along with a slightly lower speed. Note the difference. If worse, try the opposite, and experiment with different combinations until you feel you have found the best possible combination. Practice this at every opportunity and soon it will become second nature.
For boaters who do not own a trimmable outboard or sterndrive, I will briefly describe an alternative process that can somewhat duplicate trim action. You very likely have trim tabs. Tabs were initially developed to correct a boat that lists to one side. If the boat lists to port, lower the port tab and the boat will right itself. But if operated together, tabs can also alter the fore and aft angle of a boat. Lowering both tabs will raise the stern and lower the bow. Raising both tabs will pull the stern down into the water (same principle as when you let tap water run over the back of a spoon), and the bow will rise slightly. To a lesser extent, tab owners can also experiment with their tabs along with speed to find a more comfortable ride.
The most important take away on this article is the importance of your trim control. It is right up there with other important controls like your throttle and steering capabilities. That is why it is conveniently placed right under your thumb. Make the most of this miracle toggle switch and get into the habit of continually adjusting your trim the entire time that you are driving.